6502 Background: The standard treatment for post-operative high-risk patients (pts) with locally advanced squamous cell carcinoma of the head and neck (LA-SCCHN) is chemoradiotherapy with 3-weekly cisplatin (CDDP) (100 mg/m2, q3wk, 66 Gy/33Fr; 3-weekly CDDP+RT). However, one concern with 3-weekly CDDP+RT is insufficient CDDP compliance due to high-dose-related toxicities. Weekly CDDP+RT (40 mg/m2, qwk, 66 Gy/33Fr; weekly CDDP+RT) is an alternative regimen with better compliance. Here, we conducted a phase II/III trial of weekly CDDP+RT in post-operative high-risk LA-SCCHN. Methods: This is a multi-institutional randomized phase II/III trial to confirm the non-inferiority of weekly CDDP+RT (Arm B) compared with 3-weekly CDDP+RT (Arm A). The trial enrolled pts aged 20-75 years with post-operative high-risk features (microscopically positive margin and/or extranodal extension) and ECOG-PS 0-1. Pts were randomized in a 1:1 ratio to Arm A or Arm B. Primary endpoint of phase II was the proportion of treatment completion and that of phase III was overall survival (OS). A non-inferiority margin of hazard ratio (HR) was set at 1.32. Results: Between Oct 2012 and Dec 2018, 261 pts were enrolled (Arm A 132 pts, Arm B 129 pts). At the planned second interim analysis in phase III with 76/161 events, the Data and Safety Monitoring Committee recommended terminating the trial and publishing the results because the statistical boundary for OS non-inferiority had met the pre-specified stop criteria. With a median follow-up of 2.2 years in all randomized pts, 3-year OS was 59.1% in Arm A and 71.6% in Arm B with a HR of 0.69 (99.1% CI, 0.374-1.273 [ < 1.32], one-sided p for non-inferiority = 0.00272 < 0.00433). 3-year RFS was 53.0% in Arm A and 64.5% in Arm B with a HR of 0.71 (95% CI, 0.48-1.06). Regarding acute adverse events, neutropenia (≥ grade 3), increased creatinine (≥ grade 2), hearing impairment (≥ grade 2) and mucositis (≥ grade 2) occurred in 48.8%, 8.5%, 7.8% and 55.0% in Arm A and 35.3%, 5.7%, 2.5% and 59.0% in Arm B, respectively. For compliance, median total dose of CDDP was 280 mg/m2 (IQR, 250-299) in Arm A and 239 mg/m2 (IQR, 199-277) in Arm B. Total radiation dose was 66 Gy (IQR, 66-66) in both arms. Proportion of treatment completion was 93.2% in Arm A and 86.8% in Arm B. Conclusions: Weekly CDDP+RT is non-inferior to 3-weekly CDDP+RT for post-operative high-risk LA-SCCHN pts and has a favorable toxicity profile. Weekly CDDP+RT should be considered the new standard treatment option for these pts. Clinical trial information: 000009125 .
Long-term Follow-up of the RTOG 9501/Intergroup Phase III Trial: Postoperative Concurrent Radiation Therapy and Chemotherapy in High-Risk Squamous Cell Carcinoma of the Head and Neck
